(1) Field of the Invention:
This invention relates to a buckle assembly suitable for use in a vehicle seat belt, and more specifically to a buckle assembly in which the clinched anchor block or ferrule fixedly secured on a wire is press-fit to the buckle base.
(2) Description of the Prior Art:
As a method for securing a clinched anchor block on a buckle, it has been proposed to stamp the buckle base and then to clinch the anchor block together with the base vertically in both directions by means of a press or the like. This prior art method however includes a possible danger that the clinch force of the anchor block against the wire may be reduced where a channel-like buckle base is employed, since it is difficult to restrain the anchor block from expanding in the transverse directions, relative to the lengthwise direction of the buckle base, by dies due to narrow gaps between the side walls of the base and the anchor block and the anchor block may thus be allowed to expand in the transverse directions. The resulting prior art buckle assembly has a downward projection because the clinched anchor block is downwardly projected. Furthermore, it must also be necessary to pay attention to possible occurrence of cracks due to the stamping of the buckle base.
FIGS. 1 to 4 are schematic illustrations of such a conventional buckle assembly. FIG. 1 shows a buckle base 1 which has a central window 11 and a stamped portion 12. FIG. 2 is an end view in which the base is seen together with an anchor block clinched thereon from the wire side. The anchor block 2 is inserted in the window 11 of the base 1 and the wire 3 is seated in the stamped portion 12, followed by an application of pressures vertically in both directions as shown by arrows f so as to clinch the anchor block 2 on the base 1. In this prior art buckle assembly, the clinched anchor block 2 has a portion projecting downwardly from the base 1 and, as depicted in FIG. 3, the buckle 4 is protruded downwardly at a rear portion thereof. In addition, it is difficult to restrain the clinched anchor block from expanding in transverse directions by means of dies because only small gaps are left between the clinched anchor block and the side walls of the base. Accordingly, there is a danger that the clinch force of the anchor block against the wire may be reduced at portions, which are indicated by B in FIG. 4 since the anchor block may be allowed to expand in the transverse directions due to lack of any restraining forces in the directions indicated by A when the anchor block is clinched vertically in both directions as shown by f in the same drawing.
In order to avoid such a problem as mentioned above, it has also been contemplated to secure a clinched anchor block on a buckle base without clinching the former to the latter at all or excessively. Japanese Utility Model Laid-open No. 139421/1979 filed by the present assignee, NSK Warner K.K. and laid open to the public on Sept. 27, 1979 discloses connecting a clinched anchor block indirectly to the side walls of a base. Reference may also be made to U.K. Patent Specification No. 1,408,499 naming Frederick John Setters as a sole inventor and published on Oct. 1, 1975, in which two embodiments are described. According to the first embodiment shown in FIGS. 1 to 3 thereof, the bottom wall of a base is extended and bent upwardly. A window is also extended into the thus-extended portion of the bottom wall. Grooves are formed respectively in the side walls of an anchor block (i.e., ferrule). These grooves are fit over the side edges of the window to secure the anchor block on the buckle base. The other embodiment is illustrated in FIGS. 4 and 5 of the patent, in which keys or ribs are formed on the side walls of a buckle base and grooves formed in the side walls of an anchor block are fit over the keys or ribs. They are certainly free of the above-described problem, but they may not be physically strong enough as the anchor blocks are supported at rather limited points or lines.